Question

函数y=

sinx

x

的导数为（　　）

A．y′= xcosx+sinx x2	B．y′= xcosx-sinx x2
C．y′= xsinx-cosx x2	D．y′= xsinx+cosx x2

Answer 1

∵y=

sinx

x

，
∴y′=(

sinx

x

)′
=

(sinx)′•x-sinx•x′

x2

=

xcosx-sinx

x2

．
故选B．